Tetrafluorpropenes are known to be useful as monomers in the preparation of various homopolymers and copolymers. For example, U.S. Pat. No. 3,472,826 describes tetrafluorpropene as a comonomer in the production of polyethylene. U.S. patent application Ser. No. 10/694,273, which is assigned to the assignee of the present invention, discloses the use of CF3CH═CFH as a refrigerant with low global warming potential and also as a blowing agent for use in connection with the formation of various types of foams. In addition, CF3CH═CFH can also be functionalized to variety of compounds useful as intermediates for making industrial chemicals.
Several methods of preparing tetrafluoropropene compounds are known. For example, U.S. Pat. No. 6,548,719 B1 describes generally the production of a wide range of fluoroolefins by dehydrohalogenating, in the presence of a phase transfer catalyst, a compound of formula CF3C(R1aR2b)C(R3cR4d) with at least one alkali metal hydroxide, where the R substituents are as defined in the patent, provided that at there is at least one hydrogen and one halogen on adjacent carbon atoms. This patent, while disclosing a process that is efficient and useful for the preparation of numerous tetrafluoropropenes, does not disclose a process specifically for the preparation of 1,3,3,3-tetrafluoropropene.
The preparation of 1,3,3,3-tetrafluoropropene is disclosed in U.S. Pat. No. 5,986,151. This patent discloses a process comprising catalytic dehydrofluorination of CF3CH2CF2H in the gas phase to afford CF3CH═CHF. The preparation of 1,3,3,3-tetrafluoropropene is also disclosed in U.S. Pat. No. 6,124,510. This patent also discloses a process comprising catalytic dehydrofluorination of CF3CH2CF2H in the gas phase. Each of these patents has the disadvantage of being limited by the requirement of isolating 1,1,1,3,3-pentafluoropropane (“245fa”) as a starting reactant, which may be undesirable for reasons of cost, availability, and/or otherwise.
Several other methods of preparing tetrafluoropropene compounds are known. For example, U.S. Pat. No. 2,931,840 describes a reaction involving the pyrolysis of methyl chloride with tetrafluoroethylene, or alternatively of methyl chloride with chlorodifluoromethane tetrafluoroethylene. While this patent indicated that this process is capable of producing 2,3,3,3-tetrafluoropropene, there is no indication that the process is effective for producing 1,3,3,3-tetrafluoropropene. In addition, applicants have come to appreciate that the process described in this patent has the disadvantage of requiring in every case the use of methyl chloride as a reactant. More particularly, it will be relatively difficult to remove unreacted methyl chloride from the reaction product stream since the boiling point of methyl chloride (−24° C.) is relatively close to the boiling point of the desired 2,3,3,3-tetrafluoropropene (−28° C.).
The production of 2,3,3,3-tetrafluoropropene by a pyrolysis reaction is also disclosed in U. S. Pat. No. 4,086,407. The process disclosed in this patent has the disadvantage of requiring the use of a relatively complex and uncommon compound, namely, 1-trifluoromethyl-1,2-trifluorcyclobutane, as the starting material for the pyrolysis reaction. Furthermore, like U. S. Pat. No. 2,931,840 described above, the '407 patent does not disclose that the process is effective for the production of 1,3,3,3-tetrafluoropropene.